[SRU][B][PATCH] UBUNTU: SAUCE: iio: humidity: hts221: Fix sensor reads after resume

[Shrirang Bagul]

BugLink: https://bugs.launchpad.net/bugs/1863732

AV_CONF register (RH & TEMP. oversampling ratio's) and CTRL1 register
(ODR & BDU settings) values are lost after suspend.

While the change in AV_CONF updates the sensor resolution modes
(overriding the user configuration before the device went to suspend);
loss of the contents of the CTRL1 register leads to failure in reading
sensor output.

This patch restores the AV_CONF & CTRL1 registers after resume.

Already submitted upstream for both 4.17.y and 4.14.y (LTS) and under
review:
4.17.y: https://marc.info/?t=152455871600007&r=1&w=2
4.14.y: https://marc.info/?t=152506242000001&r=1&w=2

However, the issue is only affecting the Dell GW and not ST micro devel. boards.

Fixes: ffebe74b7c95 (iio: humidity: hts221: avoid useless ODR reconfiguration)

linux-oem buglink: https://bugs.launchpad.net/bugs/1769658

Signed-off-by: Shrirang Bagul <shrirang.bagul at canonical.com>
---
 drivers/iio/humidity/hts221_core.c | 31 ++++++++++++++++++++++++++++--
 1 file changed, 29 insertions(+), 2 deletions(-)

diff --git a/drivers/iio/humidity/hts221_core.c b/drivers/iio/humidity/hts221_core.c
index daef177219b6..7d24e3d8fbdf 100644
--- a/drivers/iio/humidity/hts221_core.c
+++ b/drivers/iio/humidity/hts221_core.c
@@ -671,13 +671,40 @@ static int __maybe_unused hts221_resume(struct device *dev)
 {
 	struct iio_dev *iio_dev = dev_get_drvdata(dev);
 	struct hts221_hw *hw = iio_priv(iio_dev);
+	const struct hts221_avg *avg;
+	u8 data, idx;
 	int err = 0;
 
+	/* Restore contents of AV_CONF (RH & TEMP. oversampling ratio's) */
+	avg = &hts221_avg_list[HTS221_SENSOR_H];
+	idx = hw->sensors[HTS221_SENSOR_H].cur_avg_idx;
+	data = avg->avg_avl[idx];
+	err = hts221_update_avg(hw, HTS221_SENSOR_H, data);
+	if (err < 0)
+		goto fail_err;
+
+	avg = &hts221_avg_list[HTS221_SENSOR_T];
+	idx = hw->sensors[HTS221_SENSOR_T].cur_avg_idx;
+	data = avg->avg_avl[idx];
+	err = hts221_update_avg(hw, HTS221_SENSOR_T, data);
+	if (err < 0)
+		goto fail_err;
+
+	/* Restore contents of CTRL1 (BDU & ODR) */
+	err = hts221_write_with_mask(hw, HTS221_REG_CNTRL1_ADDR,
+				     HTS221_BDU_MASK, 1);
+	if (err < 0)
+		goto fail_err;
+
+	err = hts221_update_odr(hw, hw->odr);
+	if (err < 0)
+		goto fail_err;
+
 	if (hw->enabled)
 		err = hts221_write_with_mask(hw, HTS221_REG_CNTRL1_ADDR,
 					     HTS221_ENABLE_MASK, true);
-
-	return err;
+fail_err:
+	return err < 0 ? err : 0;
 }
 
 const struct dev_pm_ops hts221_pm_ops = {
-- 
2.17.1